TABLE 871 (continued) 6^0 



DEFINITIONS OF UNITS 



FOOT-POUND. The work which will raise one pound one foot high. 



For conversion factors see page 251. 

 FOOT-POUND ALS. The English unit of work = foot-pounds/g. 



For conversion factors see page 251. 

 EQUATION OF TIME. Excess of mean time over true time. 

 ERG. c.g.s. unit of work and energy = one dyne acting through one centimeter. 



For conversion factors see page 251. 

 FLUIDITY. Reciprocal of viscosity, 

 g. The acceleration produced by gravity. 



GAUSS. A unit of intensity of magnetic field = 1 e.m.u.— J X ior 10 e.s.u 

 GRAM. See page 6. 



GRAM-CENTIMETER. The gravitation unit of work = g. ergs. 

 GRAM-MOLECULE = x grams where x = molecular weight of substance. 



GRAVITATION CONSTANT = G in formula G ^? = 666.4 X io' 10 dyne • cm 2 • g" 2 . 



HEAT OF THE ELECTRIC CURRENT generated in a metallic circuit without self- 

 induction is proportional to the quantity of electricity which has passed in coulombs 

 multiplied by the fall of potential in volts, or is equal to (coulombs X volts)/4.i8i in 

 small calories. 

 The heat in small or gram-calories per second = (amperes 2 X ohms)/4.i8i = volts 2 / 

 (ohms X 4. 181) = (volts X amperes)/4.i8i = watts/4.181. 



HEAT. Absolute zero of heat = — 273? 18 C. 



HEFNER UNIT. Photometric standard ; sec page 334. 



HENRY. Unit of induction. It is " the induction in a circuit when the electromotive force 

 induced in this circuit is one international volt, while the inducing current varies at the 

 rate of one ampere per second " = io 9 e.m.u. = 1/9 X io" 11 e.s.u. 



HORSEPOWER. The English and American horsepower is denned by some authorities 

 as 550 foot-pounds per second and by others as 746 watts. The continental horsepower 

 is defined by some authorities as 75 kilogrammeters per second and by others as 736 

 watts. Sec page 251. 



JOULE. Unit of work = io T ergs. For electrical Joule see page xlv. 

 Joules = (volts 2 X seconds) /ohms = watts X seconds = amperes 2 X ohms X sec. 

 For conversion factors see page 251. 



JOULE'S EQUIVALENT. The mechanical equivalent of heat. See page 86. 



KILODYNE. 1000 dynes. About 1 gram. 



KINETIC ENERGY in ergs = grams X (cm/sec.)'/*. 



LITER. See page 6. 



LOSCHMIDT NUMBER. Number of molecules per unit vol. ideal gas at o° C and 

 normal pressure, 2.705 X io 19 cm" 3 . 



LUMEN. Unit of flux of light-candles divided by solid angles. 



MEGABAR. Unit of pressure = 1,000,000 bars = 0.987 atmospheres. 



MEGADYNE. One million dynes. About one kilogram. 



METER. See page 6. 



METER CANDLE. The intensity of lumination due to standard candle distant one meter. 



MHO. The unit of electrical conductivity. It is the reciprocal of the ohm. 



MICRO. A prefix indicating the millionth part. 



MICROFARAD. One-millionth of a farad, the ordinary measure of electrostatic capacity. 



MICRON, (fi) = one-millionth of a meter. 



MIL. One-thousandth of an inch. 



MILE. See pages 5, 6. 



MILE, NAUTICAL or GEOGRAPHICAL = 6080.204 feet. 



MILLI-. A prefix denoting the thousandth part. 



MOLE. Mass equal to molecular weight of substance, 



Smithsonian Tables 



